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More Carbon Dioxide is not necessarily good for plants.

Posted on 18 April 2011 by villabolo

An argument, made by those who deny man made Global Warming, is that the Carbon Dioxide that is being released by the burning of fossil fuels is actually good for the environment. Their argument is based on the logic that, if plants need CO2 for their growth, then more of it should be better. We should expect our crops to become more abundant and our flowers to grow taller and bloom brighter.

However, this "more is better" philosophy is not the way things work in the real world. There is an older, wiser saying that goes, "Too much of a good thing can be a bad thing." For example, if a doctor tells you to take one pill of a certain medicine, taking four is not likely to heal you four times faster or make you four times better. It's more likely to make you sick.

It is possible to help increase the growth of some plants with extra CO2, under controlled conditions, inside of greenhouses. It is based on this that 'skeptics' make their claims. However, such claims are simplistic. They fail to take into account that once you increase one substance that plants need, you automatically increase their requirements for other substances. It also fails to take into account that a warmer earth will have an increase in deserts and other arid lands which would reduce the area available for crops. 

Plants cannot live on CO2 alone. They get their bulk from more solid substances like water and organic matter. This organic matter comes from decomposing plants and animals or from man made fertilizers. It is a simple task to increase water and fertilizer and protect against insects in an enclosed greenhouse but what about doing it in the open air, throughout the entire Earth?

What would be the effects of an increase of CO2 on agriculture and plant growth in general? The following points make it clear.

1. CO2 enhanced plants will need extra water both to maintain their larger growth as well as to compensate for greater moisture evaporation as the heat increases. Where will it come from? Rainwater is not sufficient for current agriculture and the aquifers they rely on are running dry throughout the Earth (1, 2).

On the other hand, as predicted by Global Warming, we are receiving intense storms with increased rain throughout of the world. One would think that this should be good for agriculture. Unfortunately, when rain falls down very quickly, it does not have time to soak into the ground. Instead, it builds up above the soil then floods causing damage to the crops. The water also floods into creeks, then rivers, and finally out into the ocean carrying off large amounts of soil and fertilizer.

2. Unlike Nature, our way of agriculture does not self fertilize by recycling all dead plants, animals and their waste. Instead we have to be constantly producing artificial fertilizers from natural gas which will eventually start running out. By increasing the need for such fertilizer you will shorten the supply of natural gas creating competition between the heating of our homes and the growing of our food. This will drive the prices of both up.

3. Too high a concentration of CO2 causes a reduction of photosynthesis in certain of plants. There is also evidence from the past of major damage to a wide variety of plants species from a sudden rise in CO2 (See illustrations below). Higher concentrations of CO2 also reduce the nutritional quality of some staples, such as wheat.

4. The worse problem, by far, is that increasing CO2 will increase temperatures throughout the Earth. This will make deserts and other types of dry land grow. While deserts increase in size, other eco-zones, whether tropical, forest or grassland will try to migrate towards the poles. However, soil conditions will not necessarily favor their growth even at optimum temperatures.

5. When plants do benefit from increased Carbon Dioxide, it is only in enclosed areas, strictly isolated from insects. However, when the growth of Soybeans is boosted out in the open, it creates major changes in its chemistry that makes it more vulnerable to insects, as the illustration below shows.

Figure 1: Plant defenses go down as carbon dioxide levels go up, the researchers found. Soybeans grown at elevated CO2 levels attract many more adult Japanese beetles than plants grown at current atmospheric carbon dioxide levels. Science Daily; March 25, 2008. (Credit: Photo courtesy of Evan Delucia)

Figure 2: More than 55 million years ago, the Earth experienced a rapid jump in global Carbon Dioxide levels that raised temperatures across the planet. Now, researchers studying plants from that time have found that the rising temperatures may have boosted the foraging of insects. As modern temperatures continue to rise, the researchers believe the planet could see increasing crop damage and forest devastation. Science Daily; Feb. 15, 2008.

Figure 3: Global Warming reduces plant productivity. As Carbon Dioxide increases, vegetation in Northern Latitudes also increases. However, this does not compensate for decreases of vegetation in Southern Latitudes. The overall amount of vegetation worldwide declines 

In conclusion, it would be reckless to keep adding CO2 to the atmosphere. Assuming there are any positive impacts on agriculture in the short term, they will be overwhelmed by the negative impacts of climate change.

It will simply increase the size of deserts and decrease the amount of arable land. It will also increase the requirements for water and soil fertility as well as plant damage from insects.

Increasing CO2 levels would only be beneficial inside of highly controlled, enclosed spaces like greenhouses.

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Comments 1 to 50 out of 228:

  1. I wonder why Nature has managed to make an increase of average temperature bad for everything. Isn't it quite unlikely ?
    especially for agriculture, it is quite weird because each plant has a favorite biotope, so the productivity cannot be a universal decreasing function of the local average temperature. So it must be somewhere optimal. But changing temperature should only displace the location of the optimum. Well it could be that this displacement is unfavorable, but also it could be the opposite. How do you explain that it seems to be *universally* unfavorable, everywhere? and if not, how can you properly compute an average trend, and know whether the benefits are larger than drawbacks or the opposite ?

    you seem to possess some kind of science I'm totally ignoring ....
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  2. My oh my, Gilles - your trolling is becoming more and more blatant.

    The initial post contains reasons, references, and data supporting the premise. Your post contains vague handwaving, zero references, and indicates that you have either not read the initial post or references, or are completely and deliberately ignoring them.

    Assertions without evidence can be dismissed without evidence - your post is content free, trolling, and should be treated as such. DNFTT.
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  3. I often use the analogy of extra calories. How's that McDonalds diet working out for the average American's health?

    I agree that a simplistic view that rising CO2 is good for plants, without taking into account other nutritional requirements not to mention the effects of climate change on trees is a willfully obtuse denier tactic.

    On the other hand, the FACE experiments do show increased growth in the field, as does this study from the Smithsonian.

    http://www.sciencedaily.com/releases/2010/02/100201171641.htm

    Unfortunately, what the FACE results find, and my own investigation into that Smithsonian research

    (posted here http://witsendnj.blogspot.com/2010/04/serc-sucks.html)

    indicate is that any boost in growth is more than offset by stunting from concurrent rises in the level of background tropospheric ozone. Ozone results from the same processes of burning fuel that produce CO2 and climate change. Ozone is itself a greenhouse gas but even more significantly, it is toxic to vegetation. It reduces annual crop yield and quality by anywhere from 20% to 80%, according to various international agencies, making this an urgent problem right up there with ocean acidification. Trees exposed to cumulative damage season after season are dying at a rapidly accelerating rate. Without trees as CO2 sinks, climate change will lurch ahead in very hazardous ways.

    Many studies link increased damage from secondary attacks from insects, disease and fungus as well as storm and drought to ozone, not CO2. Here is an excerpt from an article about FACE (Free Air Carbon Dioxide Enrichment) program in Wisconsin:

    http://www.admin.mtu.edu/urel/news/media_relations/49/

    The trees of the future may be much more vulnerable to a variety of pests, say scientists studying greenhouse gases in northern Wisconsin forests. Their work is published in the Nov. 28 edition of the journal Nature.

    Researchers in the Aspen FACE (Free-Air Carbon Dioxide Enrichment) Experiment, based in Rhinelander, Wis., have been measuring the effects of elevated levels two greenhouse gases, carbon dioxide and ozone, on aspen forest ecosystems. While the trees, Populous tremuloides (trembling aspen), seem to do relatively well in a carbon dioxide-rich atmosphere, ozone is another story.

    Trees growing in an ozone-enriched atmosphere have been hit much harder by their traditional enemies: forest tent caterpillars, aphids and the rust fungus Melampsora.

    "This has been a surprise," said Professor David Karnosky of Michigan Technological University's School of Forest Resources and Environmental Science, a principal investigator on the Aspen FACE project. "Our experiment was never meant to look at pest occurrence. But it became obvious that the greenhouse gases were affecting the abundance of pests."

    Ozone seems to be a special blessing to aphids. Not only did the tiny insects thrive in high-ozone air, populations of aphids' traditional predators--such as ladybugs and spiders--plummeted. "The aphids had free rein," noted Caroline Awmack, an Aspen FACE researcher from the University of Wisconsin, Madison, Department of Entomology.

    Studies have shed some light on why the aspen growing in ozone-rich air were turning into so much bug salad: their leaves seem to be undergoing fundamental changes. "Ozone alters the surface waxes," said Kevin Percy, a research scientist with Natural Resources Canada--Canadian Forest Service, who is the lead author of the Nature article, "Altered Performance of Forest Pests under Atmospheres Enriched by C02 and O3."

    The number of aphids increased about five-fold in plots with elevated ozone, while the number of aphid predators was cut in half. In plots with elevated levels of both carbon dioxide and ozone, the aphid population tripled, while the number of natural enemies increased slightly, mitigating the aphids' effect on the aspen.

    Melampsora infection in the control and CO2-enriched plots was about the same, but increased about 400 percent in the O3 plots and doubled in the plots with extra CO2 and O3. The number of forest tent caterpillars increased by about one-third in the O3 plots and actually decreased slightly in the CO2 plots and the plots with extra CO2 and ozone.

    Links to more research can be found here: http://witsendnj.blogspot.com/p/basic-premise.html
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  4. KT there is no assertion - except I'm surprised by the general result - that everything goes wrong. Obviously agriculture is a complicated aggregation of several things , very variable locally - temperature, rains, ground chemical composition, CO2, parasites ... Under some conditions, CO2 is actually used to improve the growth. So you wouldn't expect that a CO2 increase is bad *everywhere* Do you think that God hates us so much ?
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  5. "The initial post contains reasons, references, and data supporting the premise"

    AFAICS, the initial posts contains a short list of possible reasons that could go worse. This is neither exhaustive, nor limitative. There is no figures associated. No possibility of doing any budget. No experimental validation on a global scale. I can't see how to draw a general conclusion from that ..
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  6. Gilles@4 The article does not say that "everything goes wrong", just that CO2 is only beneficial "plant food" if conditions are right (i.e. growth is not limited by water supply, soil quality or pests). However the rise in temperature expected due to the rise in CO2 is likely to reduce water supply in many places, reduce soil quality and benefit pests. That means on balance, the additional carbon dioxide is likely to be bad for plants. That does not mean that there will not be any plants that will benefit from the additional CO2.

    God doesn't hate us so much, the natural environment is increasingly the way we have made it, the responsibility is ours.
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  7. Giles, #4:
    "Obviously agriculture is a complicated aggregation of several things , very variable locally - temperature, rains, ground chemical composition, CO2, parasites ... "

    Which is why the claim "More Co2 will be good for plants" is so wrongheadedly simplistic. It ignores everything else that also affects plant growth.

    "So you wouldn't expect that a CO2 increase is bad *everywhere*"

    Nobody said it was.
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  8. OK so is your point that despite the increase of CO2, the overall productivity could decrease at some places ?

    or is it that the aggregated effect all over the world will be negative, because you can make an overall budget of all possible positive and negative effects everywhere ?
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  9. "Plants cannot live on CO2 alone."

    Agreed.

    "They get their bulk from more solid substances like water and organic matter."

    As I understand it, they get approximately half their "bulk" from Carbon. Much of the rest comes from Oxygen.
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  10. Gilles@9 You are over-interpreting the article again. The point it makes is that "CO2 is plant food" argument is over-simplistic, and that if you look at the next level of detail up, there is good reason to think that rises in CO2 may well be bad on balance for plant life. The article does not address the next level of detail up from there, which would be to do the research needed for a global study from which you could estimate a budget. There is a good reason why not, which is that the "CO2 is plant food" is adequately dealt with by qualitative arguments that demonstrate that it is simplistic. There is also the fact that the research is the task of the research community, the task of SkS is communication of that research to the general public and to provide a forum for members of the general public to discuss it at an appropriate level of complexity.

    Now as I said, if you are interested in budgets etc., go and find them for yourself and let us know what you find. We will be interested to hear about it.
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  11. Gilles (@ #1), according to evolutionary development, life adjusts as well as it can (given its existing forms in any historical moment) to changing conditions. If the changes come slowly and are limited in space, many forms have the chance to adapt. If the changes come rapidly and are general, some forms are unable to adjust, and they become extinct. Feedbacks then occur in the food chain. Now consider the number and changes (and their breadth and depth) brought about by the rapid expansion of the human population in a mere 200 years. The ecosystem is undergoing multiple deep, broad, and rapid changes (habitat destruction, rapid warming, increasingly acid oceans from CO2, other forms of pollution, migration interference, water availability changes, colonization and destruction of "food animals"--fish, cows, pigs, et al.-- etc.), and you say it's unlikely that it's all bad?

    And Gilles, "god" - really? Good grief. *looks at watch* God's late. Should we start without him?
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  12. Gilles
    It's not bad for everything. It's good for the pests, as the article said.

    On a separate note, perhaps a good response to the 'plants will absorb the extra CO2 as it is plant food" is to point out that the level of CO2 has demonstrably risen, which means the plants are not aborning the 'excess'. And there has been no massive increase in plant fecundity in the past 100 years, besides that attributed to the use of modern farming techniques.

    So exactly when are the plants expected to take advantage of this free food bonanza?
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  13. This article makes a lot of predictions as if they were proven fact. That is not the case. I am amazed that any number of catastrophic scenarios can be attributed to "excess" CO2 and not one single positive benefit has been presented.
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  14. 15 Seaward - Possibly a good point, possibly not.

    May I suggest you present some documented evidence of how plants do better with higher levels of CO2 - what those levels are, what other factors (water supply, nutrients etc.) are required to support that advantage, etc. With a few decent references, I'm sure it'd be a good contribution.
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  15. "there is good reason to think that rises in CO2 may well be bad on balance for plant life."

    "The ecosystem is undergoing multiple deep, broad, and rapid changes (habitat destruction, rapid warming, increasingly acid oceans from CO2, other forms of pollution, migration interference, water availability changes, colonization and destruction of "food animals"--fish, cows, pigs, et al.-- etc.), and you say it's unlikely that it's all bad?"

    Excuse me, but am i wrong or in the past century, CO2 concentrations, temperature, and agricultural productivity have all increased together ? is it not a definite proof that it cannot always be true that increasing CO2 will be bad "on balance"?

    (I think you will agree that in simple logics, it is enough to find a single counterexample to show that a thing is not always true?)

    So if it is not always true, do you know a little bit more specifically under which conditions it will be true ?

    stating that it "may" be wrong (or true) is of course not falsifiable. But do you have a more precise idea of what it will be - and when ?
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  16. Whats going on here?
    I earlier posted a response to the recently created (April 14th) "CO2 is plant food" thread, and instead of responding, the author then duplicates his claims made there in a this brand new thread.
    ???
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  17. Villabolo, making an argument that CO2 is merely plant food is understating the fact.
    Carbon is a fundamental building block for all life forms, plants being about 45% carbon, whilst animals including humans are less than 20%.
    Interestingly, by comparison the carbon content of coal ranges from about 30% in low rank coals such as lignite to 45% to 85% for the most used form of bituminous coal, up to to 98% in anthracite.
    However what I am interested in is the statement "Higher concentrations of CO2 also reduce the nutritional quality of some staples, such as wheat."
    Are you able to quantify both the reduced nutritional quality along with any associated increased yields as determined by the better performing varieties that have been tested in open field trials under enriched CO2 conditions?

    Apart from that, some points in the OP are confusing and in apparent conflict.
    For example, the concerns made about the extra requirements of plants bought about by increased CO2 becoming a limiting growth factor, seems to have been overcome by point 3 where resultant denser vegetation apparently creates increased fire risk.

    What position is being asserted, less growth due to various limiting factors, or denser growth?
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  18. Re " any number of catastrophic scenarios can be attributed to "excess" CO2 and not one single positive benefit has been presented.

    The article is simply being true to the headline:

    "Too much of a good thing is a bad thing. Increasing Carbon Dioxide, as 'plant food', is not good for plants."

    Elsewhere on SkS both the pros and cons of increasing CO2 and temperatures have been discussed-- sorry, but cannot find that link right now.

    The science and body of evidence strongly indicate the the cons far outweigh the pros, for a net negative impact on agriculture and ecosystems and ultimately us.
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  19. @ Gilles "it cannot always be true"

    Sure I could construct a scenario where CO2 increases are on balance positive... but that scenario would be markedly different from what we are currently experiencing. So you point is completely irrelevant. Increasing CO2 brings with a very large number of changes. Some are good, and some are bad. But the best estimates at quantifying the good and bad show that the bad is far greater than the good.
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  20. Change apparently affects diversity. I remember reading a recent study addressing why there is so much more species diversity in the tropics as opposed to temperate climates. The conclusion of the study was that the absence of seasons promoted diversity. Even though seasons move in a generally predictable manner, the annual changes were still enough to discourage species diversity. Change by itself seems to be enough to powerfully affect how many species will survive.

    Thus adding CO2 quickly to the environment, changing the amount of water falling or the amount of water available, changing temperature ranges, etc., should be expected to lower diversity in the short term. In the long term, nature can be expected to adjust, once the changes stop. That may be in hundreds or thousands of years, Gilles.

    So do we put our civilization on hold until then, or stop the worst of it now?
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  21. For everyone else I suggest a quick brush up on Liebig's law of the minimum which states that plant growth is controlled not by the total amount of resources available, but by the scarcest resource.

    Or in other words, no amount of CO2 will turn the Sahara green
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  22. I do think that this argument could be expressed in terms 'denialists' can understand because they use them so often:

    The impact on vegetation his highly uncertain, to predict it one would have to depend on models, the measurements of vegetation, globally, are incomplete and historically depend on proxies... bla bla bla... we can't know if increasing CO2 is good or bad, there's uncertainty and consequentially we should do everything to stop adding CO2 to the atmosphere.

    :)
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  23. "Plant defenses go down as carbon dioxide levels go up, the researchers found. Soybeans grown at elevated CO2 levels attract many more adult Japanese beetles than plants grown at current atmospheric carbon dioxide levels."

    Perhaps, to look at it another way, it's not the plants "defenses" that go down, but the plants "appeal" that goes up?
    Perhaps a healthy plant is more attractive to an "adult Japanese Beetle" than an unhealthy one starved of CO2.
    Perhaps a healthy plant would appeal to beetles of every nationality and not just Japanese ones?

    Perhaps it would mean that a well-fed Japanese beetle would be more appealing to a Japanese birdy?
    Perhaps the whole food chain would be more healthy?
    Perhaps increased CO2 is good for ALL life on earth?
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  24. This is an interesting topic. I get the feeling that several aspects may have been glossed over (as necessary for a blog post) -- one of these is the conclusion that more water will be necessary for plants in a higher CO2 world. Because the stomata won't need to be open so long (due to the higher CO2 availability), there will be less evapotranspiration per carbon molecule fixed. At least, that's one hand-waving argument. Has this been worked out in detail?
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  25. "Increasing CO2 brings with a very large number of changes. Some are good, and some are bad. But the best estimates at quantifying the good and bad show that the bad is far greater than the good."

    It's just about plant growth here - and it's not "scenarios", just known facts :CO2 has increased, and agricultural production has increased as well.
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  26. "Increasing CO2 levels would only be beneficial inside of highly controlled, enclosed spaces like greenhouses".

    I see. This is why global carbon content of both soil and vegetation is increasing exponentially during the last 150 years. In spite of widespread destruction of woodland. Sounds plausible.

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    Response: [DB] Those wishing to see the original, in-full-context version of BP's above graph can find it here: http://maps.grida.no/go/graphic/carbon-stocks-trends-and-projections-compared-to-1860.

  27. Vegetation was carbon-free in 1860 ???
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  28. Gilles: "Excuse me, but am i wrong or in the past century, CO2 concentrations, temperature, and agricultural productivity have all increased together ? is it not a definite proof that it cannot always be true that increasing CO2 will be bad 'on balance'?"

    I'll bite by stating the obvious counterargument: You're saying that increased atmospheric CO2 caused the increases in 20th century agricultural productivity?

    Unintentionally, of course, you are correct. The FF-powered tractor has caused a tremendous increase in agricultural productivity in the last 100 years. FF have also allowed for the cheap production and delivery of pesticides and herbicides, advanced seeds (I should say "advanced" when I think of Monsanto), and advanced agricultural machinery. I think--and I'm just guessing here (sorry scientists)--that such things far outweigh any currently theorized positive effect of CO2 on plant growth where agricultural productivity during the 20th century is concerned.
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  29. @1 Gilles:

    " wonder why Nature has managed to make an increase of average temperature bad for everything. Isn't it quite unlikely ?"

    "Why am I not surprised that Gilles would be the first commenter on my post?

    No, it's not going to be bad for everything. Just those things that survive. It'll only take a few tens of thousands of years for evolution to enable plants that don't fair well with increased CO2 (Assuming they don't become extinct for ther AGW related issues).


    "especially for agriculture,it is quite weird because each plant has a favorite biotope, so the productivity cannot be a universal decreasing function of the local average temperature. So it must be somewhere optimal. But changing temperature should only displace the location of the optimum. Well it could be that this displacement is unfavorable, but also it could be the opposite. How do you explain that it seems to be *universally* unfavorable, everywhere? and if not, how can you properly compute an average trend, and know whether the benefits are larger than drawbacks or the opposite ?"(Underlining mine)

    You seem to be on both sides of the fence as to the favorability/unfavorability of biotope shifting on agriculture. At least we agree that changing the temperature will shift the location of where the crops would grow (optimally, of course).

    It's real simple. How many 100s of millions of people are going to be migrating northward (in a civilized manner, of course)?


    "you seem to possess some kind of science I'm totally ignoring ...."

    Science? This is actually in the realm of common sense deductions based on the conclusions of science.
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  30. "You're saying that increased atmospheric CO2 caused the increases in 20th century agricultural productivity? "

    Noooo, I'm just saying it didn't prevent it.

    "The FF-powered tractor has caused a tremendous increase in agricultural productivity in the last 100 years. FF have also allowed for the cheap production and delivery of pesticides and herbicides, advanced seeds (I should say "advanced" when I think of Monsanto), and advanced agricultural machinery. I think--and I'm just guessing here (sorry scientists)--that such things far outweigh any currently theorized positive effect of CO2 on plant growth where agricultural productivity during the 20th century is concerned."

    and yet the idea is to suppress FF ... to avoid CO2 to hinder productivity ... ??
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  31. @ 17 Johnd:

    Whats going on here?
    I earlier posted a response to the recently created (April 14th) "CO2 is plant food" thread, and instead of responding, the author then duplicates his claims made there in a this brand new thread.


    I know there is a redundancy Johnd but that is not due to anything I did. This is the first thread that I noticed, so I've been here all along.

    If there's a problem you can take it up with one of the moderators or John Cook.
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  32. @5 Gilles:

    "AFAICS, the initial posts contains a short list of possible reasons that could go worse. This is neither exhaustive, nor limitative. There is no figures associated. No possibility of doing any budget. No experimental validation on a global scale. I can't see how to draw a general conclusion from that .."

    That is why we have Intermediate and Advanced levels, Gilles.

    As far as experimentation on a global scale, why the Hades would that be needed? We can learn all we need to know from a few experiments and draw general conclusions as to what would happen globally.
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  33. @30 Gilles:

    "You're saying that increased atmospheric CO2 caused the increases in 20th century agricultural productivity? "

    Noooo, I'm just saying it didn't prevent it."

    For one who is very much into quantifying things to death, let me ask you, Gilles; what level of CO2 increase can be tolerated by plants until a point is reached that noticeably effects them?

    It's not likely to be a gradualistic or linear incline. It could be like the proverbial straw that broke the camel's back.

    Besides, do you know the levels of CO2 that where used in the experiments which gave the dramatic results? They are likely to be much higher than our current C2 levels.

    Of course, those levels are doing nothing but going up.
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  34. @Berényi Péter #26

    I'm saying it again: Add 24 dollars and you'll get Manhattan.

    Where did you get that figure? "Source: Based on ...."?

    Can you explain how come from 1860 to 2010 that the content of carbon in soils increased? What kind? Where? (Location, level)

    How come the value of carbon in soils increased when agriculture by using chemical fertilizers and irrigation has obtained crops in a soil increasingly impoverish in humus so the black rich soil in years back has become nowadays that brownish or yellowish thing.

    A group of people debated some months ago (in Spanish) about this general subject and information was presented about some 6GTons of Carbon lost from soils just from the Pampas, and some other +2Gtons lost from the Chacos during the last century, just in part of my country -those regions totals some 0.7% of emerging lands-. In vegetation, the lost of mass in the Chacos is enormous and maybe we can estimate it in some 0.4 to 0.6 GT of Carbon (35 million of hectares of 20-25 meters high forests with very old trees has been reduced to grassland, bushland and seasonal agriculture).

    Again, are the soils becoming increasingly dark by humus or the Carbon is kept in some strange chemical process? Could you explain. Your image is very hard to believe. Some 70GT of increment in Carbon content for some roughly 100 million square kilometers of emerging lands -excluding Antarctica, Greenland, deserts, inland waters, rocky places, and the like- is some 0.7kg per square metre, so a volume of some 2-3-4 litres of humus has been add to every m2 of black to reddish soil, dry bald grasslands and under human pavement. How come? Can you elaborate? Can you state the source and why you judged it to be appropriate for this site and for this subject?
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  35. I agree with Alec @34, and I'd recommend taking it further, if one if going to post images at SkS two things:

    1) They should be cited/sourced and a link to the original report or journal paper should be provided. Context is very important.
    2) They should not be rooted by a bizarre site like this as BP's image is.
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  36. @30 Gilles:

    ""The FF-powered tractor has caused a tremendous increase in agricultural productivity in the last 100 years. FF have also allowed for the cheap production and delivery of pesticides and herbicides, advanced seeds (I should say "advanced" when I think of Monsanto), and advanced agricultural machinery. I think--and I'm just guessing here (sorry scientists)--that such things far outweigh any currently theorized positive effect of CO2 on plant growth where agricultural productivity during the 20th century is concerned."

    This is off topic so my response is going to dead end with this post.

    Our agriculture is definitely not"advanced" but destructive.

    1. Soil erosion of six feet in what used to be prairie. This is due to soil exposure that monoculture inevitably creates.

    2. The quality of food has been going down for decades. It's been tested for nutrient levels for that long.

    3. As far as pesticides and herbicides are concerned, they are overused and would not even be need with truly advanced horticulture.

    Do some research on Permaculture, Gilles. It is self fertilizing like nature. Why deplete oil reserves that should be conserved for plastic production?

    Permaculture is also, by design, very resistant to pests. It eliminates soil erosion and it provides optimum quality food by restoring and increasing the fertility of our depleted soils.

    You are operating from the assumption tat this is the best of all possible worlds. It is not and FF is actually contributing to its demise even when you take GW out of the picture.
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  37. @ Gilles "CO2 has increased, and agricultural production has increased as well."

    Yes, but most likely the increase in CO2 is not responsible (again see Liebig's law of the minimum). But more to the point, as was stated in the second paragraph of this post "Too much of a good thing can be a bad thing."

    The effects on climate by CO2 over the past100 years have been small compared with what we expect for the next 100 years under BAU. Which means that the correlation you are so fond of is not likely to continue.

    Or to summarize, no amount of CO2 will make the Sahara green.
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  38. Strange evolution we have, don't we? The plants are not optimized for a 280ppm level of CO2 imposed to them during millennia, but for the 395ppm actual one and they have yet more to give as they are expecting the level to reach 500, 600, any advance on 700ppm? just to thrive.

    Even stranger evolution: all plants will equally thrive, the big ones, the small ones, even in lichens, the photosynthetic partner will increase the pace and the mycobiont will follow singing "heigh-ho! heigh-ho! ..." ... it will be heaven in earth!! Alleluia!

    The fact is that gene pools in every species contain most everything it's necessary to face changes provided there are not so many things changing at the same time and given enough time. Is that factor being taken into account? Everything is good if CO2 raises to 1000ppm in 10,000 years? 1,000 years? 100 years? 25 years? How come any underground line brings me home?

    How does a species to know that it needs to adapt to 800ppm CO2, 5°C more and dryer conditions, or just adapt to 800ppm CO2 and move from Baja California to Anchorage? Will it have time enough to move as in previous occasions? Do Tijuana, San Diego, Los Angeles, San Francisco, Portland, Seattle and Vancouver let it move naturally?
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  39. villabolo at 06:59 AM, strange you didn't notice the other thread as you have 3 separate posts in it.

    Anyway are you going to address the matters I repeated in this thread in "johnd at 05:17 AM" with connection to your assertions, particularly to quantifying your claims about declining nutritional values of foods grown for human consumption, past present and future.
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  40. Several additional points from things I have read in the past - sorry know references, just memory.

    Increased CO2 levels can result in reduced numbers of Stomata on leaves - with more CO2 available they don't need as many to supply the same metabolic rate. Paleoclimatologists use stomata counts on fossil leaves as a method of estimating past CO2 levels.

    Stomata are used for evapotranspiration so this may reduce water loss, but this also provides the plants principle source of cooling, so changed stomata count may impact a plants ability to thermo-regulate - an issue in a hotter and certainly more variable climate.

    Temperature limits are important to plants. They can do quite well up to some temperature limit then declines markedly - the tree-line on any mountainside is the most obvious example of this.

    With more CO2 available a plant may be able meet its 'food' needs with less consumption of its resources freeing it up to devote more resources to other functions such as protection from predators through the production of more toxins. I believe increased toxin levels have been reported in Cassava. Might we see increased caffeine levels in coffee & tea?

    Just because a plant may be able to produce more biomass from increased CO2, that does not automatically mean that this increased biomass will manifest as increased yields of the crops we eat. Our food supply is sourced predominantly from the reproductive parts of the plants. Just because a plant is doing better overall does not mean that it will therefore increase its reproductive activity. A common trait is that plants go into increased reproductive activity, more flowering etc when under stress. If the plant is thriving it might devote more resources into enhancing its own survival rather than reproduction. There could even be a reduction in yield from some plants because of this.

    Finally the response of a plant species to an environmental change can be two-fold: Adaptation to the changed environment via changes to its metabolism or Migration to remain within its preferred environment.

    The capacty of plants to adapt to an environmental change depends on whether they have the metabolic pathways and behaviours that allow that change or whether they can evolve new traits as a response. If it doesn't have the pre-existing metabolic/behavioural response availabe, then evolution is its only viable response. Which then raises the question of speed of adaptation. With the rate of CO2 change being nearly unprecedented in Earths history, how fast a plant can adapt to a change may its key survival problem. Annuals such as grains may fare better here than larger long lived species that take years to reach sexual maturity. So evolutionary rates of change could have huge impacts on the species mix of ecosystems, with all sorts of flow on effects.

    As far as migration is concerned, this again depends on mechanism and speed. Wind blown seeds that can go huge distances allow rapid migration. Seeds from fruit that drop near the parent only permit very slow migration. And just because migration speed may be sufficient to keep pace with climate shifts, that doesn't mean the other aspects of the environment they need will be available, particularly soil characteristics.

    And finally, plants face a predator that not only predates them for food, but unusually predates them very effectively if they migrate, just because they are migrating. Us. We call them weeds and kill them.

    So given the range of possible impacts on plants due to CO2 rise and temperature change, from individual plant composition to ecosystem structure, the fact that some plants may reap some benefits from increased CO2 is far more likely to be overwhelmed by the diversity of negative adaptation pressures for ecosystems.

    And since some of these ecosystems are critically important to us - we call them farm paddocks - CO2 increase is far more likely to be a negative than a positive for our food supply.
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  41. Villabolo,

    There is much material out there to satisfy the "concerns" raised by the 'skeptics' regarding the nutritional content being diminished for doubled or trebled CO2 levels.

    One of my main concerns about this post is that there was not meat in terms of referencing the scientific literature-- but some mistakenly take that to mean that such support is missing in the literature.

    Ironically enough, the only link that you provide in the body text (at point number 3 in your post) is about diminished nutritional quality in some staples, in this case wheat. I'm certain that the "skeptics" do not even bothering reading these posts, they see the title and launch into obfuscation mode.
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  42. "How do you explain that it seems to be *universally* unfavorable, everywhere?"

    Unfavorable? Only if you've got some vested interest in things being much as they have been for the last 10,000 years or so.

    Many millions of years ago, lots of little critters in a different atmospheric arrangement produced a gas that was poisonous to the biota of the time. In the end, oxygen wiped out a whole "nature" that had developed relying on little or no oxygen. In its place, we got the beginnings of the atmosphere that suits us and the other plants and animals that survive and thrive around us.

    Nature. Does. Not. Care. About anything. It's like a computer or the internet. It is just a set of processes and linkages that work regardless of what we would call the content. A computer does not know or care if it is used to create beautiful art or write a vile book or play mindless games or run a payroll or spread a 'virus' destroying the hard work of millions of people. It just follows its own rules.

    If something happens to damage or destroy some plants or animals, 'nature' does not know or care that its processes may take thousands or millions of years to establish a new set of successful items. Its got all the time in the world. Literally.

    We are the only ones that care whether our own lives or the lives of our descendants will be comfortable and successful or difficult and miserable. We are the only ones capable of caring whether the same considerations affect people we'll never know and plants or animals we will never see.
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  43. @24 Steve L:

    "This is an interesting topic. I get the feeling that several aspects may have been glossed over (as necessary for a blog post) -- one of these is the conclusion that more water will be necessary for plants in a higher CO2 world. Because the stomata won't need to be open so long (due to the higher CO2 availability), there will be less evapotranspiration per carbon molecule fixed.

    SteveL; It's refreshing to have a meaningful and rational question to respond to.

    No, it's not so much glossing over as it is keeping the post both on a basic level as well as brief (You can see how long it already is). However, to answer your question from a non-scientist's view, let me make some inspired attempts.

    Even if plants should become more efficient in water usage they are still likely to require more water. Perhaps in lesser proportion compared to other factors but more nonetheless.

    Likely to be of more importance is the increase in soil evaporation. This would effect agriculture due to the soil being exposed. Also when the temperature gets too hot for the plant's basic metabolism, aquifer fed sprinklers would have to be used to cool them down. Aquifers are getting depleted throughout the world.

    Metaphorically speaking, there is a spider web pattern of effects when you pull just one thread.
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  44. This post on CO2 is dreadfully simplistic and naive.

    In the Australian context of savanna woodlands increased vegetation in terms of trees will decrease not increase fire. Grass is what makes fire carry in the world's vast area of savanna biomes.

    Most detailed crop physiology modellers will now take CO2 fertilisation into account when simulating crop growth. If there is enough water and nutrients growth will be enhanced. At the levels of CO2 enhancement practically experienced in the field is CO2 really having any impact of yield quality?

    At a whole landscape scale increased CO2 will improve transpiration efficiency and greater water runoff will result.

    Climate change will have winners and losers. If North America became warmer and wetter - their wheat yields would be boosted considerably, especially with some CO2 turbo-charging.

    As for more intense rainfall causing greater loss of soils and nutrients - I wonder - there is this thing called soil conservation - contour banks, minimum tillage or zero tillage. Great advances have been made in these areas over the last 40 years.

    What could have been mentioned at the other end is that CO2 can increase frost sensitivity (deniers would chip in here and exclaim it will never frost again).

    Anyway the case for winners and losers needs to be made. At nation state level, land use, biome, and ecological patch level. The article here is far too simplistic.
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  45. @39 Johnd:

    "villabolo at 06:59 AM, strange you didn't notice the other thread as you have 3 separate posts in it."

    I did post on what I assumed was a blog post that had not been officially turned in a post for public view. As I said, this is the first post I noticed today, when I went to home page. I assumed that anything on this post would supersede any previous posts. Sorry for any misunderstandings.

    As for declining nutrition in wheat, mentioned in my rebuttal above, I provided a link. As to other comments on nutritional deficiencies due to mass produced agriculture (Non CO2 related), that was an off topic comment in response to the claim that FF based agriculture is "advanced". I'd rather leave that particular issue at that.

    Right now I'm backed up with two other responses as well as personal chores, so I can't respond to every question; particularly if they're not directly in reference to CO2 issues.
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  46. @41 Albatross:

    "One of my main concerns about this post is that there was not meat in terms of referencing the scientific literature-- but some mistakenly take that to mean that such support is missing in the literature."

    Albatross, John C previously stated, in response to someone with your own concerns on references, that it was not necessary for a Basic Level post to provide such references. The articles cited in the illustrations do provide such sources.

    In any case, I'll be adding extra primary source references as time allows; but there is no need to elaborate in the main text due to its basic level.
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  47. Berényi Péter - That's a fascinating chart, Berényi. Why did you clip it?



    This is from a set of Hadley Center forest predictions, discussing climate change effects on forests. Unfortunately, there is no discussion of that chart in the PDF.

    One interesting factoid from that PDF - during the 2003 heat wave in Europe, crop productivity dropped 30%. Climate change doesn't seem to be good for crops...
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  48. Moderators - What are the ethics of a carefully clipped chart (pretty obviously edited) without attribution?
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    Moderator Response:

    [DB] Given that less than 10% of all readers ever click on an obviously provided link, when said hyperlink is incorporated into an expandable thumbnail (Admission: I hyperlink scaled thumbnails for brevity sake; but I do not only present PART of the original image) with the only way of knowing it IS hyperlinked is to mouse over it/move the cursor over it...you tell me.

    Not warning the reader that the enclosed graphic is an enlarged, windowed version of a much larger graphic certainly opens up the reader to the possibility of taking the totality of the graph out of its intended context.

    In like fashion, it certainly opens up the poster of the questionably presented graphic to many, many questions...

  49. KR,

    Smile. Good sleuthing. There goes BP'S already troubled credibility. I hope that people following this thread note that this is the kind of thing that climate scientists and others who understand AGW to be a concern repeatedly come up against. The 'skeptics' demonstrate highly questionable ethics, yet repeatedly falsely accuse others of same.

    Again, this is not so much about where things stand now, but where we are headed if we continue on this path consumption.
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  50. villabolo at 09:45 AM, just FYI the other thread was available from the time you first made it. I noticed it then,but didn't have time to respond, only earlier seeking it out again to follow up. Perhaps you should have it removed entirely as it only serves to clutter and confuse.

    The only link you provided is to an abstract regarding, IIRC, a laboratory study. I believe I have read some of that paper somewhere previously.
    However, given we are talking about the real physical world, laboratory studies are of limited value. At the very least it should be the results of FACE trials that you are referencing as these provide the closest data simulating future real world conditions.
    But more important than that they are the only means by which modeling based on laboratory experiments are able to be validated.
    It appears that the FACE trials indicate that the results produced under real world conditions differ from the expectations of the modeled laboratory projections, requiring the models to be retrained against the results obtained under FACE conditions.
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